单项选择题
A.氮B.磷C.钾D.硼
A.树冠投影半径的1/3倍处至滴水线附近B.干基附近C.树冠投影半径的1/3范围内D.树冠投影半径的1/3倍处
A.60~100cmB.40~60cmC.70~110cmD.80~120cm
A.3~6cmB.1~2cmC.7~10cmD.10~15cm
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